Sex Differences in Running Performance Among 8-and-Under and 9-10-Year-Old Children in US Regional Track Championships.

Males aged 8-and-under ran significantly faster than females across all running distances examined.

• Males (n=2696 race times) ran 3.8%-5.9% faster than females (n=2710) across all distances.
• Differences were statistically significant (p<0.001) with effect sizes of Hedges' g=0.39-0.63.
• Events examined included 100m, 200m, 400m, 800m, and 1500m.
• Data were collected from all 15 USATF Regional Championships held in 2022-2024.

Males aged 9-10 years ran significantly faster than females across all running distances examined.

• Males (n=3265) ran 3.4%-5.5% faster than females (n=3182) across all distances.
• Differences were statistically significant (p<0.001) with effect sizes of Hedges' g=0.31-0.52.
• Events examined included 100m, 200m, 400m, 800m, and 1500m.
• Data were collected from all 15 USATF Regional Championships held in 2022-2024.

The fastest individual males outperformed the fastest individual females by a meaningful margin across events and age groups.

• The fastest individual males outperformed the fastest individual females by 1.8%-11.6% across events and age groups.
• This was evaluated by comparing performances at the 95th percentile and top individual finishers.
• The range of differences varied across the five distances (100m, 200m, 400m, 800m, 1500m) and two age groups.

Sex-based performance differences were consistent across the full spectrum of competitor ability, not just at elite levels.

• Performance differences were evaluated across the 95th, 90th, 75th, 50th, 25th, and 10th percentiles.
• Across percentiles, males ran on average 4.4% ± 1.2% faster than females.
• The consistency across percentiles indicates that the performance gap is not limited to the top competitors.

Prior literature had reported minimal sex-based differences in running performance before age 11, but this study found clear differences at ages 8-10.

• Prior studies have often focused on elite performers or record holders, potentially neglecting trends across the full competitive field.
• Some prior studies reported minimal sex-based differences before age 11.
• The current study used all official race times from preliminary and final races across 15 regional championships from 2022-2024 to capture the full competitive field.
• Two-way ANOVA with p<0.05 threshold was used to compare race times by sex.